Electric circuit arrangement



April 12, 1960 L. A. RICE ELECTRIC CIRCUIT ARRANGEMENT Filed Nov. 5, 1956 QIIHIIII INVENTOR. Lyman .4. Rice H/ls Altar/7 ey United States Patent ELECTRIC CIRCUIT ARRANGEMENT Lyman A. Rice, Anderson, Ind., assigmor to General Motors Corporation, Detroit, Mich., a corporation of Delaware Application November 5, 1956, Serial No. 620,287

1 Claim. (Cl. 317141) This invention relates to a delay circuit for an electromagnetic relay and is more particularly concerned with a circuit arrangement which will cause the opening of the switch contacts of a relay to be delayed for a short period of time after the circuit to the relay actuating coil is broken.

Various arrangements for delaying the opening of the switch contacts responsive snap-acting switches are frequently used in connection with relay actuating circuits to delay the opening of the contacts. Another arrangement which is employed comprehends the use of a magnetic slug or shorted turn in the relay magnetic circuit. While either of these arrangements are satisfactory for certain purposes, it has been found that each are limited in their application. More particularly, the thermally responsive snap-acting switches will provide too great a time delay and the magnetic slug will provide an insuflicient delay. The present invention is directed to an arrangement which will provide a delay that is in the order of A to A of a second and, therefore, will operate in a range unattainable in the devices heretofore known.

In view of the above, it is, therefore, an object of the present invention to provide an inexpensive means which will delay the opening of a relay for a short period of time after the energizing circuit to the magnetic coil of a relay is broken.

A further object of the present invention is to use an incandescent lamp as a means for delaying the opening of the switch contacts of an electromagnetic relay.

A still further object of the present invention is to arrange an incandescent lamp in a relay circuit so the lamp is normally deenergized and is energized for a short period of time only during which time the lamp will operate to delay the opening of the contacts of a relay after the energizing circut to the relay actuating coil is broken.

Further objects and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawing wherein a preferred embodiment of the present invention is clearly shown.

In the drawing:

The single figure shows a circuit diagram incorporating the delay circuit for a relay invention.

In the drawing, the numeral 20 indicates a source of electrical energy, such as a storage battery. The battery 20 has one of its terminals grounded at 22 and has its other terminal connected through a lead 24 to a junction 26. An electromagnetic relay of the conventional type is provided with an iron core 28 and a coil winding 30, which has one of its ends grounded at 22 and has its other end 32 connected through a normally open switchaccording to the present Well known. For example, thermally I 2,932,774 Patented Apr. 12, 1960 ing means 34 with junction 26. The relay is also provided with a pair of normally open switch contacts 36 and 38. In the embodiment shown, the contact 38 is carried by the relay armature 40, which is arranged to be moved Whenever the coil winding 30 is energized as when switch 34 is closed so that contacts 38 and 36 engage one another. A load, designated by the numeral 42, is connected through a lead 44 with the stationary contact 36 of the relay. From the above arrangement, it is apparent that whenever switch 34 is closed, current will flow from the source 20 through the actuating coil 30 of the relay so that the armature 40 will be magnetically attracted by the core 28 and moved against the force of spring 46 so that the contacts 38 and 36 move into engagement to complete the circuit between the source 20 and the load 42, which is grounded at 22. Further, whenever the switch 34 is open, the energization of the coil winding 30 will be immediately broken so that the contacts 36 and 38 will instantly separate.

The present invention is directed to a means for delaying the opening of the contacts 36 and 38 for a short when initially energized, will have a low resistance. The

value of this resistance will rapidly increase with the increase of the temperature of the lamp filament due to its heating by the current flowing therethrough. Thus, in

the circuit arrangement shown, whenever switch 34 and switch contacts 36 and 38 are closed, the lamp 48 will remain deenergized because both terminals of the lamp will be at the same voltage potential. When, however, the switch 34 is initially opened, switch contacts 36 and 38 will remain closed for a short period of time, which will range from A to A of a second. This delay will occur as the circuit is completed from the source 2.0 through the closed switch contacts 36 and 38, lead 50, lamp 48 through the coil winding 39 to ground 22. This will permit the energization of the magnet core 28 to continue until the resistance and voltage drop across lamp 48 increases sufliciently until the current flow through coil 30 is insufficient to cause the attraction of core 28 to overcome the force of spring 46 on armature 40. The period of time required for the resistance of lamp 48 to increase to cause the opening of the contacts will range from to A of a second so that the load will be supplied with electrical energy from the source 24) for a period of time after the switch 34 is opened.

While the embodiment of the present invention as herein disclosed, constitutes a preferred form, it is to be understood that other forms might be adopted.

What is claimed is as follows:

A time delay circuit for maintaining circuit continuity between a voltage source and a load for as long as a 3 r cuit for said relay coil including said manually operable switch, said relay coil being continuously energized sufficiently to maintain said relay contacts closed and said load energized as long as said manually operable switch is closm, a second energizing circuit for said relay coil including said relay switch contacts and the filament of said lamp, said second energizing circuit maintaining said relay coil energized sufiiciently to maintain said relay switch contacts closed and said load energized for a short ,period of time following the opening of said manually operable switch and the consequent 'openingof said first energizing circuit.

References Cited in the file of this patent UNITED STATES PATENTS ol Oct. 5,1931 Mott July 7, 1936 Peters July 5, 1938 Baker Feb. 1, 1944- 'FOREIGN PATENTS Switzerland Feb. 18, 

